As a healthcare professional, it is important to understand the difference between “drug repurposing” and “drug repositioning.” The terms are often used interchangeably but can have different processes and regulatory implications in drug development. Here, you will learn about the differences between the two terms with real-world examples of repurposed drugs and repositioned drugs.
What is the difference between “drug repurposing” and “drug repositioning”? While both processes aim to extend the utility of drugs, their specific focus, origins, and regulatory implications may differ. Because there are no officially approved definitions of these terms, they are often used interchangeably. This sometimes creates confusion, slows down processes, and hinders opportunities for collaboration in drug development and research.
A study by researchers at Utrecht University found only about 31% of articles using the terms “drug repositioning” and “drug repurposing” provided a definition, leaving 69% without definition. The definitions provided ranged from brief to extensive, but no common definition was found, which often leads to differences in meaning. The study suggests that in cases where a clear definition is required, such as for legal or regulatory purposes, further clarification is needed.
Although these two definitions differ, they both aim to utilise existing drugs in drug development, provide a cost- and time-efficient solution, and explore new therapeutic indications. Both processes can offer a quicker and more affordable path to treatment for unmet medical needs.
Recently, using drug repurposing and repositioning as strategies has become more common as researchers focus on expanding the uses of existing drugs. Advances in artificial intelligence and big data analytics have significantly increased the speed and success of identifying new uses for existing drugs. However, unexpected repurposing can occur, particularly through clinical observations or unexpected findings during trials.
Continue reading to gain a deeper understanding of the difference between drug repurposing and drug repositioning:
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What is Drug Repurposing?
Drug repurposing often refers to identifying new therapeutic uses for drugs that have already been approved for specific conditions.* These drugs have undergone rigorous testing for safety and efficacy, which reduces the time and resources needed to assess their potential for other diseases. By leveraging the established safety profiles of these drugs, repurposing offers a more efficient path to developing treatments for other indications.
This process accelerates the drug development timeline and reduces overall costs, as the drug has already passed extensive clinical trials and is familiar to regulatory bodies. As a result, repurposed drugs can often be brought to market more quickly, making them a valuable tool for addressing unmet or emerging medical needs.
What is Drug Repositioning?
Drug repositioning often refers to taking drugs originally developed for a specific condition but shelved due to safety concerns, regulatory hurdles, or failure to meet clinical trial objectives.* Some drugs may have passed clinical trials and received regulatory approval but are shelved for reasons such as lack of funding, market saturation, intellectual property issues, or changes in business strategy. These drugs can be re-evaluated to determine if they could be useful for treating other diseases.
The key difference between drug repositioning and drug repurposing is that repositioning involves drugs that were abandoned or shelved, whereas repurposing typically involves drugs that are still in use but being tested for new indications. Repositioning can involve drugs being tested for new uses within the same or even a different therapeutic area. This approach allows researchers to save time by utilising existing clinical data, though overcoming previous safety or efficacy concerns can be a challenge.
Key Benefits of Drug Repurposing and Drug Repositioning:
Both drug repurposing and drug repositioning offer significant cost and time efficiencies. Since the drugs are already developed and have undergone safety testing, both processes can shorten the drug development timeline and reduce costs compared to developing a new drug from scratch.
Both strategies allow for faster access to treatments for diseases with unmet medical needs, especially when urgent therapies are required. By leveraging existing drugs, both approaches have the potential to improve patient outcomes quickly, using therapies that have already demonstrated some level of safety and effectiveness. This strategy was extensively explored and implemented during the COVID-19 pandemic as part of the emergency response.
Main Differences:
- Drug repurposing tends to be faster and more straightforward because the drugs are still actively used in the market and have established safety profiles. This means repurposed drugs can be brought to market more quickly, often benefiting from expedited approval processes for new indications.
- Drug repositioning, on the other hand, may involve shelved drugs that failed in earlier trials or were abandoned for safety or commercial reasons. While drug repositioning can offer new therapeutic benefits, it may be slower and more complex due to the need to address previous safety or efficacy concerns. However, repositioning allows for a more targeted approach, re-evaluating drugs that were once dismissed, potentially providing new treatments for diseases.
Key risks of Drug Repurposing and Drug Repositioning:
Both drug repurposing and drug repositioning involve using existing drugs to treat new conditions, but they carry similar risks related to efficacy, safety, and regulatory approval. For both processes, the primary concern is whether the drug will be effective for its new indication and its potential market value.
Although the drug may have been tested for safety in its original use, unanticipated side effects or drug interactions can arise when used for different diseases. Additionally, both processes face regulatory hurdles, as new trials and data may be needed to gain approval for the new use.
Main Differences:
- Repurposed drugs generally have a more established safety profile, which means the risk to patients is somewhat lower compared to repositioned drugs. However, repurposing still carries the risk that the drug may not work for the new condition, have unexpected side effects, or it could face market competition from established treatments.
Drug repurposing for COVID-19 faced several challenges, leading to risks to patient safety.* Drugs used for malaria and Ebola were proposed based on early-stage studies or theoretical benefits, but larger clinical trials often failed to confirm their effectiveness. Despite insufficient evidence, some medications were promoted as treatments. The lack of solid data, unclear dosing information, drug interactions, hasty regulatory approvals, and public confusion all contributed to adverse outcomes.* - Repositioned drugs often face higher risks if they were originally shelved due to unresolved safety or efficacy concerns, rather than commercial factors like market saturation. Drugs with a commercial history of failure may struggle to secure funding or regain market confidence. For drugs that failed due to safety or clinical concerns, repositioning may require more extensive regulatory scrutiny compared to already approved drugs being repurposed for new indications.
The case of TGN1412 illustrates the risks of drug repositioning.* Initially developed as an immunotherapy for cancer in the early 2000s, it was shelved after severe adverse effects in early trials. Attempts to reposition it for autoimmune diseases in 2006 failed due to unresolved safety concerns, leading to its discontinuation for all uses. This underscores the risks of using drugs with prior safety issues, as these concerns can prevent success in new indications.
Examples of Drug Repurposing and Drug Repositioning
Drug Repurposing Examples:
- Ketamine for Depression*
Repurposed Use: In 2019, the FDA approved esketamine, a nasal spray formulation of ketamine’s active S-enantiomer, for the treatment of treatment-resistant depression. The treatment offers a faster-acting alternative to traditional antidepressants and is typically used in conjunction with an oral antidepressant for patients who do not respond to other treatments.
- CAR-T Cell Therapy for Lupus*
Repurposed Use: A small clinical trial in 2022 showed promising results using CAR-T cell therapy to treat lupus. It is currently being explored as a potential treatment for autoimmune diseases, including lupus, due to its ability to target specific immune cells. However, more research is needed to determine its long-term safety and efficacy for lupus.
Drug Repositioning Examples:
- Sildenafil for Pulmonary Hypertension*
Original Use: Sildenafil was developed in the early 1990s as a treatment for angina (chest pain) and was initially tested in clinical trials. However, it was shelved after initial trials showed it did not effectively treat angina.
Repurposed Use: During clinical trials for angina, researchers noticed a side effect: sildenafil caused erections in male participants. This observation led to repositioning the drug for erectile dysfunction, resulting in the approval of Viagra in 1998. Further studies showed sildenafil’s effectiveness for pulmonary hypertension, leading to its approval for this use in 2005. It has since become a widely used treatment, significantly improving patients’ quality of life.
- Thalidomide for Multiple Myeloma*
Repurposed Use: In the 1990s, thalidomide was repositioned for the treatment of multiple myeloma, a type of blood cancer, after studies showed it had anti-inflammatory and anti-cancer properties. Thalidomide was approved in 2006 for the treatment of multiple myeloma and other cancers, significantly improving patient outcomes when used in combination with other therapies.
Were you aware of the differences between drug repurposing and drug repositioning as a doctor? Let us know your thoughts on the topic in the comment section below.
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